Book/Report

FZJ-2019-03745

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Magnetische Kopplungsphänomene in epitaktischen Schichtsystemen aus Eisen und dem ferromagnetischen Halbleiter Europiumsulfid

Rücker, U. (Corresponding author)FZJ*

1998
Forschungszentrum Jülich, Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/22416

Report No.: Juel-3541

Abstract: Europium sulphide (EuS) is a ferromagnetic semiconductor with a Curie temperature of 16 K. The lattice mismatch between EuS and Fe is 3.7%. With thermal evaporation in ultrahigh vacuum it is under suitable conditions possible to grow thin EuS films epitaxially on Fe films, that are prepared on a GaAs (100) single crystal with a Ag buffer layer. In the following it is possible to put another epitaxial Fe layer on top of the EuS. With Auger spectroscopy it is confirmed that at least six monolayers of EuS grow layer by layer on Fe. In the LEED image a good long-range order is observed, RBS-Channeling investigations reveal a minimum yield down to 6% in a 167 nm thick EuS layer on Fe, but this value increases to more than 20% close to the interface. A relaxation of the lattice mismatch is observed within the first 50 nm of the EuS layer. In double layers Fe I EuS antiferromagnetic coupling at the interface of the two different ferromagnetic materials is observed. The coupling appears together with the ferromagnetic order in the EuS film and increases linearly with decreasing temperature. At 7 K the coupling strength is J = -0.19 mJ/m$^{2}$. In triple layers Fe / EuS / Fe ferromagnetic coupling between the Fe layers is observed at all temperatures 7 K $\le$ T $\le$ 300 K and interlayer thicknesses 0 $\le$ d $\le$ 5 nm. For quantitative measurement of the ferromagnetic coupling strength the spin engineering technique with an extended layered system Fe / Cr / Fe / EuS / Fe is used. At all temperatures an exponential decay of the coupling strength with increasing interlayer thickness is observed. Strength and range of the coupling are strongly temperature dependent: The range of the coupling has a maximum at 17 K. Below 20 K it is in the order of 1 nm, above 50 K it is constantly 0.25 nm. The coupling strength is minimal at 17 K, it increases strongly to lower as well as to higher temperatures. The increase of the coupling strength at higher temperatures is exponential. This behaviour is caused by two different coupling mechanisms that are active in different temperature regimes. At low temperatures, below the Curie point of EuS, the EuS layer is coupled to both adjacent Fe layers and transmits a long-range coupling through the ferromagnetic order in the interlayer. The coupling at high temperatures can be described by coupling through the thermally excited electronic system of the semiconducting interlayer, as it has been predicted by theoretical calculations.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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